A global navigation satellite system (GNSS) utilizes an earth-orbiting constellation of a plurality of satellites each broadcasting GNSS signals which indicates its precise location and ranging information. From particular locations on or near the earth, GNSS receivers may detect valid GNSS signals and take various GNSS measurements such as pseudorange, carrier phase, and/or Doppler to calculate navigation information such as GNSS receiver position, velocity, and time. The American global positioning system (GPS), the Russian global orbiting navigation satellite system (GLONASS), are examples of GNSSs.
GPS satellites transmit. L-band carrier signals continuously in two frequency bands, L1 band (1575.42 MHz) and L2 band (1227.60 MHz), respectively. The GPS satellites transmit GPS signals using code division multiple access (CDMA) technique that transmits different GPS codes on same frequency. The unique content of each GPS code is used to identify the source of a received signal.
GLONASS satellites transmit L-band carrier signals in two frequency bands, L1 band and L2 band, respectively. The GLONASS satellites transmit the same code as their L1 band signal, however each transmits on a different frequency using a 21-channel frequency division multiple access (FDMA) technique spanning from 1598.0625 MHz to 1609.3125 MHz. The relationship (1602+n×0.5625) MHz is utilized to determine the exact center frequency, where n is a satellite's frequency channel number (n=−7, −6, −5, . . . , 13). The L2 signals use the same FDMA technique, but transmit between 1242.9375 MHz and 1251.6875 MHz. The relationship (1246+n×0.4375) MHz is utilized to determine the center frequency of the L2 signals, where n is a satellite's frequency channel number (n=−7, −6, −5, . . . , 13).
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.